All -


I have a question related to surface mount component coplanarity.

Is there a set +/- "window of opportunity" that surface mount gull-wing
leads are allowed to fall within?  Is this covered in a standard anywhere?

I looked into IPC-A-610 and J-Std - and I found information related to "toe
down" configuration but I did not see any information related to "toe up"
configuration.

I also referenced JESD22 Method B 108.  Interesting guideline - using the
seating place method as a measure of determining coplanarity deviation.  So,
if I am understanding this test method properly, the user (meaning the
manufacturer trying to build with the darn thing) defines the +/- window?

Background info:
Qualifying new board.  One part on the board is a large transformer with
gull wing leads - 24 leads on either side of the component.  We are
frequently seeing leads bent upwards (towards the heavens) and this is
obviously creating manufacturing frustrations.  However, vendor is
indicating a +/- window of 4 mils - either side.  Doesn't that seem large?
That would be a total of 8 mils of variation.....

So, I was just wondering if there was a criteria out there that we could
reference, to determine whether or not these parts are really acceptable.


Appreciate the help.

- D

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